Combustion chamber



July 20, 1943.

J. 5. HUBER COMBUSTION CHAMBER Filed July 24, 1940 N x M 3 4 Z a 2 III IL {I 0 w Z a v /A 7 J \4. h P Q! 6 N fl//// 4% :J// 4 aways. QUEERPatented July 20, 1943 COMBUSTION CHAMBER John S. Huber, South.Milwaukee, Wis., assignor to Nash-Kelvinator Corporation, Kenosha, Wis.,

. a corporation of Maryland Application July 24, 1940, Serial No.347,088

3 Claims.

This invention relates to combustion chambers of lntemal combustionengines and has particular reference to the shape of a combustion cham-V ber of a valve-in-head engine.

It is an object of this invention to provide a combustion chamber formore perfectly controlling combustion in a valve-in-head engine.

It is another object of this invention to provide a combustion chamberin which the fuel m xture is less liable to detonate, causing the engineto knock.

It is another object of this invention to provide a combustion chamberwhich will function smoothly in a dual ignition engine. a

It is another object of this invention to provide a piston which isco-operable with the head of a valve-in-head engine to forma novelcombustion chamber.

Other objects and advantages of'this invention will be apparent from aconsideration of the'following description and claims and the attacheddrawings of which there is one sheet andln which- Figure 1 represents avertical, transverse, sec tional view through a cylinder of an internalcombustion engine of the valve-in-head type;

Figure 2 represents a sectional view taken along planes indicated by thebroken lines 2--2 in Figure 1 and looking in the direction of thearrows;

Figure 3 represents a perspective view of the top of the pistonillustrated in Figures 1 and 2;

Figure 4 represents a graph in which the ratio of the volume of unburnedfuel to the/surface surrounding that volume is plotted against the timeof burning in the combustion chamber.

It is generally understood that the fuel charge in an internalcombustion engine does not normally explode all at once, but burns alonga generally spherical flame front, the center of which is located at thesparkplug. In dual combustion engines, two flame fronts are startedconcurrently and are propagated at! approximately equal rates throughthe fuel, charge. These spherical flame fronts first intersect in thecenter of the chamber leaving pockets of unburned fuel toward the sidesof the cylinder, which charges are liable to detonate due to theincreased pressure in the chamber. This results in a knock in theengine. This invention deals with means for overcoming this undesirablefeature. The spark plugs of the engine have been moved as far apart aspossible so that the flame fronts are more nearly flat when theyintersect, thus leaving smaller pockets of unburned fuel. The piston hasbeen so shaped on its upper surface rings 22.

as to increase the area of piston and head surface surrounding the finalunburned charge so that as the heat within the combustion chamberincreases due to the compression of the partially burned fuel charge,the increased surface will absorb more heat from the unburned charge,thus preventing it from reaching its detonation temperature.

Figure 1 shows an internal combustion engine having a cylinder blockgenerally indicated at ID, a piston generally indicated at It, and ahead generally indicated at I4. Within the. block l0 are formed theusual cylinders l6 surrounded by cooling water jackets I8. The piston i2is provided with the usual piston pin 20, and piston The lower wall 23of the head I4 is recessed on the underside thereof to form thecombustion chamber 24 into which a fuel mixture is led by the intakepassage 26 controlled by the valve 28. The intake passage 26 opens fromthe side of an intake manifold 30 cast along the up-" per surface of thehead 14. Positioned underneath the intake manifold 30 is a heaterchamber 32 connected to the exhaust passage 33 which discharges into theexhaust manifold 35. The intake passage, heater chamber and exhaustpassage are surrounded by cooling water space 34. Spark plugs 36 extendthrough apertures 31 in the side walls of the block l0 and project intothe sides of the combustion chamber 24. The usual type of valveactuating mechanism including the rocker arms 36, rocker arm shaft 38and push rods 40 are carried on top of the block l4 so as to open thevalves 28 against the force of the valve springs 42. a

Specifically, the combustion chamber 24 is generally oval-shaped in planview, having semicircular ends 44 (see Figure 2). This increases thelength of the combustion chamber along the line of the valves so thatlarger valve ports may be used. The sides of the chamber 24 between thesemi-circular ends 44 are curved outwardly by cutting away the lowerwall 23 in scm'-cylindrical pockets 45 which intersect the apertures 31in which the spark plugs 36 are positioned with the electrodespositioned at or near the creasing the distance between the plugs andlengthening the radius of the flame fronts.

Moving the plugs out without providing the pockets 45 is ineffectivebeyond a limit because a point is soon reached Where the small aperture31 will not be scavenged of burned gases after each charge is fired andthe efilciency of the plug is glass. The inside of the piston ishollowed out under the land 48 as at 50 (see Figure 1) to lighten thepiston.

The piston I2 is arranged to project upwardly into the combustionchamber 2% with the land portion 88 spaced slightly from the valve 28when the piston is at top dead center.

In operation, with a charge of fuel compressed in the combustionchamber, the spark plugs 36 will ignite the small initial charges in thecut away pockets G5 on the sides of the combustion chamber from wherethe flame front will pass through the major portion of the charge whichis retained between the combustion chamber walls and the cup-shapedsurfaces 5% of the piston. When the main charge has been burned, arelatively small final charge will remain between the land portions 18and the top of the combustion chamber. This final portion will have beenraised in temperature due to the increased pressure in the chamber.However, the area of the land 48 on the piston and the area of thevalves and the top of the combustion chamber surrounding the finalcharge is relatively large and sufiicient heat will be conducted awayfrom the final charge through the piston to the water cooling jacket isand through the top of the combustion chamber to the cooling jacket 3 inthe head to prevent the final charge from rising to a temperature atwhich it will detonate.

As indicated in Figure 4, in which the ratio of the volume of unburnedfuel to the surface of the chamber surrounding that volume is plottedagainst the time of burning of the entire charge, at the time ofignition the volume to surface ratio represents the total volume andtotal surface. As the small initial charge in pockets Q5 is burned, asmall volume surrounded by a relatively large surface is burned so thatthe volume to surface ratio is increased. After the main charge isburned, a small volume remains between large surfaces so the volume tosurface ratio drops rapidly to a very low value indicating achambeiwhich will extract more heat from the charge and prevent it fromdetonating as has been ex plained above. The relationship between theinitial, main and final charges in the chamber and the surfacessurrounding those charges will not be the same in all engines to getmaximum power and smoothness from the engine. For instance, differentengines with diiierent size pistons and compression ratios will operatemost efficiently with different volume to surface ratio curves. Thuswhile the shape of the combustion chamber could be determined by using aflat top piston and shaping the top wall of the chamber under thecylinder head, it is much cheaper to use a flat top chamber and obtainthe desired shape of chamber by cutting away the piston. This makes iteasier to design the intake and exhaust ports and valves for a flat topchamber, while the correct chamber shape may be determined by experimentwith pistons cut in different shapes.

While I have described by invention in some detail, I intend thisdescription to be an example only and not as a limitation or myinvention in which I make the following claims:

1. In an internal combustion engine, a cylinder block having cylindersformed therein, a cylinder head having combustion chambers formed on theunderside thereof, having a fiat top surface and oo-operable with saidcylinders, ignition devices for said combustion chambers, valvemechanism carried in said head and projecting through said top surface,pistons carried in said cylinders and arranged to project into saidcombustion chamhere in their uppermost positions, each of said pistonsbeing provided with a flat central upper portion projecting intoadjacency with said flat top surface of the combustion chamber and saidvalves and extending parallel thereto, each of said pistons beingprovided with oppositely-facing, and spherical-surfaced recesses in eachside, 7

the center of which is approximately at said ignition device, therecesses being disposed in the projecting portion of each piston in itsuppermost position, said ignition devices being carried by said cylinderhead opposite the recesses in said pistons, the walls of said combustionchambers being partially recessed in the vicinity of said ignitiondevices, to provide vertical, partially cylindrical surfaces.

2. A combustion chamber for a valve-in-head engine comprising a pair ofoppositely facing lateral recesses having their principal surface formedas a segment of a cylinder, a spark plug mounted in each of saidrecesses with the electrodes thereof adjacent said cylindrical surface,a pair of principal chambers, each of said recesses opening into one ofsaid chambers, each of said chambers having its major surface remotefrom said recesses formed as a portion of the surface of a sphere, saidelectrodes being located at the approximate centers of said spheres.

3. A combustion chamber for a valve-in-head engine comprising a pair ofoppositel facing lateral recesses having their principal surface formedas a segment of a cylinder, a spark plug mounted in each of saidrecesses with the electrodes thereof adjacent said cylindrical surface,a pair of principal chambers, each of said recesses opening into one ofsaid chambers, each of said chambers having its major surface remotefrom said recesses formed as a portion of the surface of a sphere, saidelectrodes being located at the approximate center of said Sphere, saidprincipal chambers being joined by a thin fiat chamber uniform in depththroughout and having an outline in plan generally similar to that of anhour-glass.

JOHN S. HUBER.

